@janhq/core API Reference

The @janhq/core package provides all the APIs, types, and interfaces needed to build Jan extensions.

Installation

yarn add @janhq/core

Import

import * as core from '@janhq/core'

Base Classes

BaseExtension

All extensions extend from BaseExtension:

abstract class BaseExtension implements ExtensionType {
  name: string
  productName?: string
  url: string
  active?: boolean
  description?: string
  version?: string

  abstract onLoad(): void
  abstract onUnload(): void

  type(): ExtensionTypeEnum | undefined
  compatibility(): Compatibility | undefined

  // Settings management
  async registerSettings(settings: SettingComponentProps[]): Promise<void>
  async getSettings(): Promise<SettingComponentProps[]>
  async getSetting<T>(key: string, defaultValue: T): Promise<T>
  async updateSettings(componentProps: Partial<SettingComponentProps>[]): Promise<void>
  onSettingUpdate<T>(key: string, value: T): void

  // Model management
  async registerModels(models: Model[]): Promise<void>

  // Installation
  async install(): Promise<void>
}

Key Methods

onLoad

() => void

required

Called when the extension is loaded. Initialize your extension here.

onUnload

() => void

required

Called when the extension is unloaded. Clean up resources here.

type

() => ExtensionTypeEnum | undefined

Returns the extension type. Return undefined for generic extensions.

registerSettings

(settings: SettingComponentProps[]) => Promise<void>

getSetting

<T>(key: string, defaultValue: T) => Promise<T>

Get a setting value by key. Returns defaultValue if not found.

updateSettings

(settings: Partial<SettingComponentProps>[]) => Promise<void>

Update one or more settings programmatically.

onSettingUpdate

<T>(key: string, value: T) => void

Called when a setting is updated by the user. Override to react to changes.

registerModels

(models: Model[]) => Promise<void>

InferenceExtension

Extends BaseExtension for inference implementations:

abstract class InferenceExtension extends BaseExtension implements InferenceInterface {
  type(): ExtensionTypeEnum {
    return ExtensionTypeEnum.Inference
  }

  abstract inference(data: MessageRequest): Promise<ThreadMessage>
}

inference

(data: MessageRequest) => Promise<ThreadMessage>

required

Perform inference on a message request and return the response.

ConversationalExtension

Extends BaseExtension for conversation management:

abstract class ConversationalExtension extends BaseExtension {
  type(): ExtensionTypeEnum {
    return ExtensionTypeEnum.Conversational
  }

  abstract listThreads(): Promise<Thread[]>
  abstract createThread(thread: Partial<Thread>): Promise<Thread>
  abstract modifyThread(thread: Thread): Promise<void>
  abstract deleteThread(threadId: string): Promise<void>
  abstract createMessage(message: Partial<ThreadMessage>): Promise<ThreadMessage>
  abstract modifyMessage(message: ThreadMessage): Promise<ThreadMessage>
  abstract deleteMessage(threadId: string, messageId: string): Promise<void>
  abstract listMessages(threadId: string): Promise<ThreadMessage[]>
  abstract getThreadAssistant(threadId: string): Promise<ThreadAssistantInfo>
  abstract createThreadAssistant(threadId: string, assistant: ThreadAssistantInfo): Promise<ThreadAssistantInfo>
  abstract modifyThreadAssistant(threadId: string, assistant: ThreadAssistantInfo): Promise<ThreadAssistantInfo>
}

AssistantExtension

Extends BaseExtension for assistant management:

abstract class AssistantExtension extends BaseExtension implements AssistantInterface {
  type(): ExtensionTypeEnum {
    return ExtensionTypeEnum.Assistant
  }

  abstract createAssistant(assistant: Assistant): Promise<void>
  abstract deleteAssistant(assistant: Assistant): Promise<void>
  abstract getAssistants(): Promise<Assistant[]>
}

Extension Types

enum ExtensionTypeEnum {
  Assistant = 'assistant',
  Conversational = 'conversational',
  Inference = 'inference',
  Model = 'model',
  SystemMonitoring = 'systemMonitoring',
  MCP = 'mcp',
  HuggingFace = 'huggingFace',
  Engine = 'engine',
  Hardware = 'hardware',
  RAG = 'rag',
  VectorDB = 'vectorDB'
}

Event System

The event system allows extensions to communicate:

const events = {
  on: (eventName: string, handler: Function) => void,
  off: (eventName: string, handler: Function) => void,
  emit: (eventName: string, object: any) => void
}

Message Events

enum MessageEvent {
  OnMessageSent = 'OnMessageSent',
  OnMessageResponse = 'OnMessageResponse',
  OnMessageUpdate = 'OnMessageUpdate'
}

Example:

import { events, MessageEvent } from '@janhq/core'

events.on(MessageEvent.OnMessageSent, (data: MessageRequest) => {
  console.log('User sent:', data)
})

events.emit(MessageEvent.OnMessageResponse, responseMessage)

Inference Events

enum InferenceEvent {
  OnInferenceStopped = 'OnInferenceStopped'
}

Core Types

Model

type Model = {
  object: string              // "model"
  version: string             // Model version
  format: string              // "gguf", "safetensors", etc.
  sources: ModelArtifact[]    // Download sources
  id: string                  // Unique identifier
  model?: string              // Model identifier (modern)
  name: string                // Human-readable name
  created: number             // Unix timestamp
  description: string         // Model description
  settings: ModelSettingParams
  parameters: ModelRuntimeParams
  metadata: ModelMetadata
  engine: string              // "llamacpp", "openai", etc.
}

type ModelArtifact = {
  filename: string
  url: string
}

type ModelMetadata = {
  author: string
  tags: string[]
  size: number                // Size in bytes
  cover?: string              // Cover image URL
  default_ctx_len?: number
  default_max_tokens?: number
}

type ModelSettingParams = {
  ctx_len?: number
  ngl?: number
  embedding?: boolean
  n_parallel?: number
  cpu_threads?: number
  prompt_template?: string
  system_prompt?: string
  temperature?: number
  top_p?: number
  top_k?: number
  // ... more parameters
}

type ModelRuntimeParams = {
  temperature?: number
  max_temperature?: number
  token_limit?: number
  top_k?: number
  top_p?: number
  stream?: boolean
  max_tokens?: number
  stop?: string[]
  frequency_penalty?: number
  presence_penalty?: number
  engine?: string
}

Thread

type Thread = {
  id: string                    // Unique identifier (ULID)
  object: string                // "thread"
  title: string                 // Thread title
  assistants: ThreadAssistantInfo[]
  created: number               // Unix timestamp
  updated: number               // Unix timestamp
  metadata?: Record<string, unknown>
}

type ThreadAssistantInfo = {
  id: string
  name: string
  model: ModelInfo
  instructions?: string
  tools?: AssistantTool[]
}

ThreadMessage

type ThreadMessage = {
  id: string                    // Unique identifier (ULID)
  object: string                // "thread.message"
  thread_id: string
  assistant_id?: string
  attachments?: Array<Attachment> | null
  role: ChatCompletionRole      // 'user', 'assistant', 'system', 'tool'
  content: ThreadContent[]
  status: MessageStatus         // 'ready', 'pending', 'error', 'stopped'
  created_at: number            // Unix timestamp
  completed_at: number          // Unix timestamp
  metadata?: Record<string, unknown>
  type?: string
  error_code?: ErrorCode
  tool_call_id?: string
}

enum MessageStatus {
  Ready = 'ready',
  Pending = 'pending',
  Error = 'error',
  Stopped = 'stopped'
}

enum ChatCompletionRole {
  System = 'system',
  Assistant = 'assistant',
  User = 'user',
  Tool = 'tool'
}

ThreadContent

type ThreadContent = {
  type: ContentType
  // For text and reasoning content
  text?: ContentValue
  // For image content
  image_url?: ImageContentValue
  // For tool call content
  tool_call_id?: string
  tool_name?: string
  input?: unknown
  output?: unknown
}

enum ContentType {
  Text = 'text',
  Reasoning = 'reasoning',
  Image = 'image_url',
  ToolCall = 'tool_call'
}

type ContentValue = {
  value: string
  annotations: string[]
}

type ImageContentValue = {
  detail?: string
  url?: string
}

MessageRequest

type MessageRequest = {
  id?: string
  threadId: string              // Thread ID (deprecated, use thread)
  assistantId?: string
  attachments: Array<Attachment> | null
  messages?: ChatCompletionMessage[]
  model?: ModelInfo
  thread?: Thread
  tools?: MessageTool[]
  engine?: string
  type?: string
}

type ChatCompletionMessage = {
  content?: string | ChatCompletionMessageContent[]
  role: ChatCompletionRole
  type?: string
  output?: string
  tool_call_id?: string
}

Assistant

type Assistant = {
  avatar: string
  thread_location: string | undefined
  id: string
  object: string                // "assistant"
  created_at: number            // Unix timestamp
  name: string
  description?: string
  model: string
  instructions?: string
  tools?: AssistantTool[]
  file_ids: string[]
  metadata?: Record<string, unknown>
}

type AssistantTool = {
  type: string                  // 'retrieval', 'code_interpreter', etc.
  enabled: boolean
  useTimeWeightedRetriever?: boolean
  settings: any
}

Settings

type SettingComponentProps = {
  key: string
  title: string
  description: string
  controllerType: ControllerType
  controllerProps: SliderComponentProps | CheckboxComponentProps | InputComponentProps | DropdownComponentProps
  extensionName?: string
  requireModelReload?: boolean
  configType?: 'runtime' | 'setting'
}

type ControllerType = 'slider' | 'checkbox' | 'input' | 'tag' | 'dropdown'

type InputComponentProps = {
  placeholder: string
  value: string | string[]
  type?: 'password' | 'text' | 'email' | 'number' | 'tel' | 'url'
  textAlign?: 'left' | 'right'
  inputActions?: ('unobscure' | 'copy')[]
}

type SliderComponentProps = {
  min: number
  max: number
  step: number
  value: number
}

type CheckboxComponentProps = {
  value: boolean
}

type DropdownComponentProps = {
  value: string
  type?: string
  options?: DropdownOption[]
  recommended?: string
}

type DropdownOption = {
  name: string
  value: string
}

Utility Functions

File System

const fs = {
  existsSync: (path: string) => Promise<boolean>
  mkdir: (path: string) => Promise<void>
  readdirSync: (path: string) => Promise<string[]>
  readFileSync: (path: string) => Promise<string>
  writeFileSync: (path: string, data: string) => Promise<void>
  rm: (path: string) => Promise<void>
  mv: (from: string, to: string) => Promise<void>
  fileStat: (path: string) => Promise<FileStat>
}

Path Utilities

const getJanDataFolderPath: () => Promise<string>
const joinPath: (paths: string[]) => Promise<string>
const baseName: (path: string) => Promise<string>
const dirName: (path: string) => Promise<string>
const getUserHomePath: () => Promise<string>
const getResourcePath: () => Promise<string>

UI Utilities

const openFileExplorer: (path: string) => Promise<void>
const openExternalUrl: (url: string) => Promise<void>
const showToast: (title: string, message: string) => void
const log: (message: string, fileName?: string) => void

Example: Complete Extension

import {
  BaseExtension,
  ExtensionTypeEnum,
  events,
  MessageEvent,
  MessageRequest,
  SettingComponentProps,
  fs,
  joinPath,
  getJanDataFolderPath
} from '@janhq/core'

export default class MyCompleteExtension extends BaseExtension {
  private dataPath: string = ''

  async onLoad(): Promise<void> {
    // Initialize data path
    const janDataPath = await getJanDataFolderPath()
    this.dataPath = await joinPath([janDataPath, 'my-extension'])

    // Create data directory if it doesn't exist
    if (!await fs.existsSync(this.dataPath)) {
      await fs.mkdir(this.dataPath)
    }

    // Register settings
    await this.registerSettings([
      {
        key: 'enabled',
        title: 'Enable Extension',
        description: 'Turn the extension on or off',
        controllerType: 'checkbox',
        controllerProps: { value: true }
      },
      {
        key: 'api_key',
        title: 'API Key',
        description: 'Your API key',
        controllerType: 'input',
        controllerProps: {
          placeholder: 'Enter API key',
          value: '',
          type: 'password',
          inputActions: ['unobscure', 'copy']
        }
      },
      {
        key: 'temperature',
        title: 'Temperature',
        description: 'Model temperature',
        controllerType: 'slider',
        controllerProps: {
          min: 0,
          max: 2,
          step: 0.1,
          value: 0.7
        }
      }
    ])

    // Listen to events
    const enabled = await this.getSetting('enabled', true)
    if (enabled) {
      events.on(MessageEvent.OnMessageSent, this.handleMessage)
    }
  }

  onUnload(): void {
    events.off(MessageEvent.OnMessageSent, this.handleMessage)
  }

  onSettingUpdate<T>(key: string, value: T): void {
    if (key === 'enabled') {
      if (value) {
        events.on(MessageEvent.OnMessageSent, this.handleMessage)
      } else {
        events.off(MessageEvent.OnMessageSent, this.handleMessage)
      }
    }
  }

  private handleMessage = async (data: MessageRequest) => {
    const apiKey = await this.getSetting('api_key', '')
    const temperature = await this.getSetting('temperature', 0.7)

    console.log('Processing message with temp:', temperature)
    // Your message processing logic here
  }
}

CLI

Extensions

API Reference

Core Library

@janhq/core API Reference

Installation

Import

Base Classes

BaseExtension

Key Methods

InferenceExtension

ConversationalExtension

AssistantExtension

Extension Types

Event System

Message Events

Inference Events

Core Types

Model

Thread

ThreadMessage

ThreadContent

MessageRequest

Assistant

Settings

Utility Functions

File System

Path Utilities

UI Utilities

Example: Complete Extension

Next Steps

Building Extensions

Examples

Build docs developers (and LLMs) love

CLI

Extensions

API Reference

Core Library

Documentation Index

​Installation

​Import

​Base Classes

​BaseExtension

​Key Methods

​InferenceExtension

​ConversationalExtension

​AssistantExtension

​Extension Types

​Event System

​Message Events

​Inference Events

​Core Types

​Model

​Thread

​ThreadMessage

​ThreadContent

​MessageRequest

​Assistant

​Settings

​Utility Functions

​File System

​Path Utilities

​UI Utilities

​Example: Complete Extension

​Next Steps

Building Extensions

Examples

Build docs developers (and LLMs) love

Installation

Import

Base Classes

BaseExtension

Key Methods

InferenceExtension

ConversationalExtension

AssistantExtension

Extension Types

Event System

Message Events

Inference Events

Core Types

Model

Thread

ThreadMessage

ThreadContent

MessageRequest

Assistant

Settings

Utility Functions

File System

Path Utilities

UI Utilities

Example: Complete Extension

Next Steps